A communication scheme used in a communication system including a plurality of communication devices may be divided into contention based communication and non-contention based communication according to how communication resources are occupied or allocated by the communication devices. In the non-contention based communication scheme, an access point (AP) or a control node for controlling the AP allocates communication resources between the communication devices and the AP. In contrast, in contention based communication scheme, communication resources are occupied through contention between the communication devices which desire to access the AP.
Carrier Sense Multiple Access (CSMA)
CSMA is a contention based communication scheme and refers to a probabilistic media access control (MAC) protocol in which a node or a communication device verifies the absence of other traffic on the same shared transmission medium (also called a shared channel) before transmitting traffic on a shared transmission medium such as a frequency band. In CSMA, a transmitting device determines whether another transmission is in progress before initiating transmission of traffic to a receiving side. In other words, the transmitting device tries to detect the presence of a carrier from another transmitting device before attempting to transmit traffic. If the carrier is sensed, the transmitting device waits for transmission in progress by another transmitting device to finish before initiating transmission thereof. Consequently, CSMA is a communication scheme based on the principle of “sense before transmit” or “listen before talk”.
Meanwhile, various radio communication technologies have developed along with advances in information communication technology. Among these, a WLAN is a radio frequency based technique for allowing a user to wirelessly access the Internet in a household, an office, or a specific service area by using a portable terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), or a smartphone. Due to increase in the number of users and activation of high-capacity multimedia services, a method for increasing data throughput in a radio communication system is needed.